1. Field of the Invention
The present invention pertains to a multiple clutch arrangement, especially to a dual clutch arrangement, which can, for example, be used for the transmission of torque in the drive train of a motor vehicle.
2. Description of the Prior Art
Drive systems which are required to transmit very high torques, that is, in the drive systems used in trucks, for example, but also to an increasing extent in passenger vehicles, include gearboxes with two gearbox input shafts, which are basically coaxial with respect to each other. The various gears of the gearbox then transmit the torque from one or another of these input shafts to an output shaft. Each of the input shafts is connected nonrotatably to a clutch disk, and torque is intbaruced into the gearbox via the one or the other of these input shafts, depending on which of the clutch disks has been frictionally engaged in the clutch and thus held nonrotatably with respect to the drive shaft such as a crankshaft. Energy storage devices, usually designed as diaphragm springs, are used in these clutches to pretension the clutch disks toward the engaged position. Each of the various clutch areas of a multiple clutch arrangement of this type, e.g., a dual clutch arrangement, has its own actuator such as a master and slave cylinder system, for example, to ensure that the clutch areas are operated in coordination with each other, that is, so that torque can be transmitted via one of the clutch areas while the other clutch area is held open and is not used to transmit any torque.
Systems of this type suffer from the problem that their actuation is comparatively imprecise, especially during the clutch-engaging operation, which means that it is extremely difficult to increase the engaging force in a precisely defined manner. There is also the problem that, if the actuators used to disengage the clutches break down, both clutch areas of the dual clutch can be held in the engaged state. If, in this situation, one of the gears in the gearbox cannot be disengaged because of, for example, heavy loads or possibly because of another malfunction, the drive train of a vehicle equipped with a system of this type would be locked, and the vehicle could no longer be towed. This could be the situation, for example, when, at a certain moment, torque is being or is to be transmitted in the gearbox via one of the gearbox input shafts, while at the same time a gear has already been engaged for the other gearbox input shaft in preparation for a shift of gears by a following changeover of the dual clutch from one clutch area to the other.